Master for monitoring fluid flow type surface roughness gages

ABSTRACT

A block-type master is described which has formed on the surface thereof a series of straight line grooves, and which in carrying out the monitoring method is placed so that the groove series extends traversely to and contained entirely within the annular flow groove in the smoothness measuring reading head. The depth of the grooves is carefully controlled to create The flow precisely corresponding to that of a given roughness standard to thus provide a ready check on the accuracy of the instrument and also a convenient indicator of the cause of the instrument inaccuracy. The configuration of the flow grooves in the master allow for precise uniformity of groove depth in manufacture thereof, while this factor and the transverse placement of the flow grooves create relative insensitivity to alignment of the master and reading head, thus allowing rapid and highly accurate and repeatable monitoring checks of operating instruments.

United States Patent [1 1 Sherman 45] July 24, 1973 [54] MASTER FORMONITORING FLUID FLOW [73] Assignee: The Bendix Corporation, Southfield,

Mich.

22 Filed: Dec. 10,1972

21 Am No.: 206,038

' Primary Examiner-Richard C. Queisser Assistant ExaminerArthur E.Korkosz Att0rneyJohn R. Benetiel et al.

[57] ABSTRACT A block-type master is described which has formed on thesurface thereof a series of straight line grooves, and which in carryingout the monitoring method is placed so that the groove series extendstraversely to and contained entirely within the annular flow groove inthe smoothness measuring reading head. The depth of the grooves iscarefully controlled to create The flow precisely corresponding to thatof a given roughness standard to thus provide a ready check on theaccuracy of the instrument and also a convenient indicator of the causeof the instrument inaccuracy. The configuration of the flow grooves inthe master allow for precise uniformity of groove depth in manufacturethereof, while this factor and the transverse placement of the flowgrooves create relative insensitivity to alignment of the master andreading head, thus allowing rapid and highly accurate and repeatablemonitoring checks of operating instruments.

4 Claims, 4 Drawing Figures PAIENIEB M2 3.147. 395

sum 2 or 2 FIGS MASTER FOR MONITORING FLUID FLOW TYPE SURFACE ROUGHNESSGAGES BACKGROUND OF THE INVENTION 1. Field of the Invention Thisinvention concerns a method of monitoring pneumatic type surfaceroughness gages and also masters for use in such monitoring methods.

2. Description of the Prior Art Pneumatic type gages which measure theroughness of surfaces of articles such as sheets of paper have long beenknown and commercially available. In these devices, a reading head isusually provided which has an annular groove therein supplied with afluid (usually air) under accurately regulated pressure. In use, thereading head is placed on the surface of the sheet and flow over annularlands defining the annular groove is a measure of the roughness of thesurface.

This flow is typically measured by very accurate column type air flowgages, usually by clusters of three such instruments to measure flowscorresponding to rough, medium, and fine textures. These gages aredesigned such that the range of flows measured by each of these isconsecutive, i.e., the low flow calibration point of the highest flowgage (corresponding to rough surfaces) is the same as the high flowcalibration of the medium flow gage (corresponding to the medium roughsurfaces) and likewise the low flow calibration point of the medium flowgage is the high flow calibration of the low flow gage (corresponding tothe least rough surface).

In use, the instruments are claibrated by diverting flow through each ofa series of calibrating orifices in each instrument andcorrespondingmaster orifices on the reading head assembly instead ofthrough the reading head, with flow through a single master andcalibrating orifice used to calibrate the amplification and float .levelof each column air gage to its high flow calibration point, and flowthrough the calibrating orifice alone used to set the low point.

This is the only check heretofore available on the accuracy of thereadings during actual gaging operations, and this method has at leastfour disadvantages: (a) It does not allow for quick monitoring of theaccuracy of the readings, as the calibration procedure, while notextremely difficult does consume a significant amount of time. (b) Sinceflow is diverted from the reading head during this calibrationprocedure, a perfectly accurate calibration can still result inerroneous readings due to reading head flows such as nicks, or wear ofthe reading head lands. Hence, errors can go undetected for relativelylong .periods of time, during which huge runs of paper production can belost. (c) If erroneous readings are detected by other means the operatoris not able to determine if such errors are due to wear or dirt in themaster or internal calibrating orifices or in the reading head, etc. (d)It does not allow convenient cross checking of the high flow point withthe low flow point be tween instruments due to the configuration of thecalibration circuit.

These difficulties have heretofore not been able to be circumvented dueto the unavailability ofa flow master capable of giving the extremelyaccurate readings necessary with a high degree of repeatability withouttime consuming monitoring set ups, or excessive manufacturing costs, asprevious attempts have required extremely accurate positioning of themaster block with respect to the reading head, and further have beenvery difficult to manufacture with the accuracy required.

Therefore, it is an object of the present invention to provide a masterand a method utilizing such a master for monitoring the readings of suchinstruments which can quickly and very accurately check the readingsthereof, and when used together with the calibration procedure willinsure accurate readings.

It is a further object to provide such a master which can bemanufactured for a reasonable cost yet provide the extreme accuracyrequired.

SUMMARY OF THE INVENTION These and other objects which will becomeapparent upon a reading of the following specification and claims isaccomplished by a block master having a series of straight groovesformed across its upper surface. This series of grooves is of a widthsuch that they are completely contained within annular flow chamber,when, in use of the master of the present invention, the master isplaced under the reading head with the grooves extending transversely tothe flow chamber, so that changes in relative position between thereading head and master within limits do not affect even slightly theflow readings.

DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of the test setup with a master placed in position under the reading head.

FIG. 2 is an elevational view in partial section of the reading head andmaster shown in FIG. 1.

FIG. 3 is a view of the section taken along the line 3-3 in FIG. 2.

FIG. 4 is a view of the section taken along the line 44 of FIG. 3.

DETAILED DESCRITPION I reading head assembly 10 is depicted, operativelyassociated with a column type air flow gage assembly 12, with a master14 according to the present invention shown in place on the reading headassembly 10.

As the reading head assembly 10 and column type air flow gage assembly12 arewell known in the art only a brief description of these will herebe given.

The reading head assembly 10 includes a reading head 16, which has anannular flow chamber 18 (FIG. 3) contained therein, adapted to besupplied with air under pressure from the flow gage assembly 12. Thereading head 16 is adapted to be realeased by a linkage 18 so as to reston the specimen to be tested (or master 14 as theease maybe) and theextent of air flow out of the annular flow chamber 18 across lands 20and 22 provides a measure of the surface roughness of the specimen.

This air is supplied via an air line 24 coupled at one end to thereading head assembly 10 to supply air to an internal passage (notshown) with communicates with the annular flow space 18. The line 24 iscoupled at the other end to a common tooling outlet 25to the threecolumn air flow gages 26, 28, and which make up the How gaging assembly12.

The air flow is measured by the position of the particular float 32, 34,or 36 of the particular flow gage which covers the particular range offlow into which the test flow falls, to an extremely accurate degree dueto the design of these instruments as is now well understood in the art.

In order to calibrate each instrument as to amplification and floatlevel, the air pressure to each gage 26, 28 and 30 is carefully adjustedto IAz psi using the manometer 38 associated with the air flow gageassembly 12. The air line 24 is then uncoupled from the reading headassembly connection and connected to one of three connections 40 in thereading head manifold 41 depending on the particular flow gage 26, 28,or 30 to be calibrated.

Each of the connections 40 places the air line in communication with apassage (not shown) containing a master orifice and in addition each ofthe calibration orifices (not shown) contained within each gage 26, 28,30 themselves, are also connected to provide a calibration circuit usedto establish the necessary amplification (using knobs 44) and floatlevel (using knob 45) of each gage. Flow through each master andcalibration orifice should be at a predetermined rate at the 1 /2 psipressure for its respective gage as indicated by the float, andappropriate amplification and float level adjustments are made in orderto obtain this reading of the float when flow is passing through therespective master and calibrating orifice.

The outlet 42 of the particular master orifice is then blocked and theindicated flow through the calibrating orifice along is then adjusted tothe lower level.

It can be appreciated from this description why this procedure, as itinvolves a special calibration circuit which does not use the readinghead itself, leads to the disadvantages noted above.

The block type flow master 14 according to the present inventionconsists of a metal block, of a very stable material such as oilhardened cold stabilized alloy steel preferably AlSl8620. Formed in thetop thereof is a pair of series of parallel straight line grooves 46extending at right angles to each other.

These grooves may be formed to be of extremely uniform depth by a formgrinding process in which all of the grooves in each series are formedat once by means of crush formed grinding wheel, of the type well knownin the art.

After forming the grooves 46, the entire upper surface of the blockmaster 14 is lapped while being checked on a calibrated standardinstrument between lapping operations until the groove 46cross-sectional area is reduced to produce flow of the correct value.

One block master 14 is made for each column type air gage 26, 28, and 30with the initial grooving such that a greater flow will occur than thatfor the high reading for the respective gage, so as to be capable ofbeing lapped to produce the proper flow.

In an actual embodiment 12 grooves each way were utilized with 45sloping sides. For the No. l or rough gage these grooves were 0.0038inches deep, for the No. 2 or medium gage the depth was 0.0018 inches,and the No. 3 or fine gage, the depth was 0.0010 inches.

The number of grooves should be selected so that for the necessary flowthe individual grooves are neither too shallow or too deep.Ifexcessivcly shallow, the uniformity of depth is difficult to achieveand the lapping operation will change the flow therethrough rather rapidly, mading it more difficult to obtain the proper flow.

Making the grooves too deep may cause the penetration of the casehardened layer, which is rather shallow for oil hardened steel, leadingto a tendency towards instability of the block. (Tool steel is notsufficiently stable in itself even though the grooves may be cut deeperwithout penetration of the case hardened layer.)

Thus, utilizing a configuration wherein different series of grooves atan angle to each other and passing through the center of the block hasthe advantage of increasing the number of grooves for this purpose,while maintaining all of the grooves transverse and contained within theconfines of the annular flow chamber 18, as can be seen in FIG. 3, whichas will be explained below, is of great significance in yielding thecorrect results. In addition, this also yields a groove configuration inwhich the groove depth is much more easily held to uniformity duringforming.

Referring to FIGS. 3 and 4, the importance of this groove configurationcan be appreciated with respect to the criticality or lack thereof ofthe position of the annular flow groove 18 with respect to the grooves46.

Since each of the series of grooves 46 is much narrower than thediameter of the inner land 22,- lateral shifting in either direction(within limits) does not open up any more area available to flow andhence variations positioning in either direction will not in theleastaffect any fluid flow out of the grooves 46 due to picking up moreor fewer grooves available for fluid flow.

Since flow is almost entirely controlled by the minimum cross-sectionalarea available for flow, the transverse positioning of the grooves 46with respect to the annular flow groove 18 in carrying out themonitoring method provides insensitivity to variations in lateralposition which result in different annular flow chamber 18 are lengthsdefined by the groove series width. This can be understood from FIG. 4wherein it can be seen that regardless of the angle of the flow chamber18 into the drawing, the area defined by the grooves-46 will remain thesame and hence the flow will be substantially unaffected.

The symmetry of the annular flow chamber 18 and the above-describedgroove series characteristics also prevents variations in flow occurringbecause of variations in angular position.

In use, the instruments are calibrated in the normal fashion, and fromtime to time, the three block type flow masters for each gage 26, 28,and 30 are inserted one at a time under the reading heads in the generalposition shown in FIG. 3 to quickly obtain an extremely accurate checkon the accuracy of the instrument.

If the proper readings are not obtained, a check of the calibration ofthe instrument is made, and if it may be calibrated to obtain the properspread of high and low values, this will indicate reading head problems,while if such spread is not obtainable, dirty or worn master orificesare indicated. 1

While the instrument could be calibrated by use of the mastersthemselves, their relative expense and wear problems indicates thattheir use as a monitoring device only as described is advisable.

Thus, it can be seen that a rapid, accurate, and inherently reliablecheck on the performance of these gages chamber when the surface is inposition against said surface, the flow master comprising an elementhaving a surface adapted to be placed against said opening, said surfacehaving two series of uniform depth grooves extending thereacrosstransversely to each other and occupying a portion of said surface, eachof said two groove series widths being less than said flow chamberopening but each of said groove series lengths being greater than saidflow chamber opening, whereby flow out of said opening through saidgrooves is unaffected by limited changes in position of said chamberopening with respect to said surface.

2. The flow master of claim 1 wherein each of said two groove serieslengths extends entirely across said element surface.

3. The flow master of claim 1 wherein the crosssectional area of saidtwo groove series is such that flow therethrough out of said chamberopening is the same as that occurring with a paper specimen of aparticular surface roughness.

4. The flow master of claim 1 wherein said grooves are straight andparallel and entirely extend across said element surface.

1. A flow master in combination with a surface characteristic measuringinstrument of the type wherein a reading head having a flow chamber andan opening therein is adapted to be placed with the flow chamber openingagainst the surface and also includes means for supply and measuringfluid flow through said flow chamber when the surface is in positionagainst said surface, the flow master comprising an element having asurface adapted to be placed against said opening, said surface havingtwo series of uniform depth grooves extending thereacross transverselyto each other and occupying a portion of said surface, each of said twogroove series widths being less than said flow chamber opening but eachof said groove series lengths being greater than said flow chamberopening, whereby flow out of said opening through said grooves isunaffected by limited changes in position of said chamber opening withrespect to said surface.
 2. The flow master of claim 1 wherein each ofsaid two groove series lengths extends entirely across said elementsurface.
 3. The flow master of claim 1 wherein the cross-sectional areaof said two groove series is such that flow therethrough out of saidchamber opening is the same as that occurring with a paper specimen of aparticular surface roughness.
 4. The flow master of claim 1 wherein saidgrooves are straight and parallel and entirely extend across saidelement surface.